Allow URL objects when starting workers

[mischnic]

Passing URL object into worker construtors/navigator.serviceWorker.register should be allowed

For example described here: https://webpack.js.org/guides/web-workers/

[mvitousek]

The documentation you linked to looks good for Worker constructors; is there documentation for SharedWorker and register?

[mischnic]

It's hard to find examples for this. The reason why passing an URL object works is that it is stringified and url.toString() just returns the "real" url. (Tthe benefit of the URL/import.meta.url thing is that the worker script is now actually relative to the JS file that creates the worker, just like an import - otherwise, it's relative to the current document. And since this URL->string conversion happens automatically, you can omit toString() in browsers.)

Webpack example for SharedWorker: https://github.com/webpack/webpack/blob/c181294865dca01b28e6e316636fef5f2aad4eb6/examples/worker/example.js#L25-L31

The arguments for Worker, SharedWorker, register are all USVString according to the spec, so URLs aren't specifically handled there (and all three should behave the same).

https://w3c.github.io/ServiceWorker/#idl-index
https://html.spec.whatwg.org/multipage/workers.html#dedicated-workers-and-the-worker-interface
https://html.spec.whatwg.org/multipage/workers.html#shared-workers-and-the-sharedworker-interface

[isker]

Worth considering: https://github.com/microsoft/TypeScript/blob/a15030ff6fd63bc0c2a9ea1fe0ade45da2ecd698/lib/lib.webworker.d.ts#L2898

[mischnic]

@mvitousek What do you think?

As far as I can tell, Flow already does what I'm proposing here for fetch: RequestInfo is the "url or request" input type for fetch:

flow/lib/bom.js

Line 1511 in f9afdbc

type RequestInfo = Request | URL | string;

flow/lib/bom.js

Line 1601 in f9afdbc

declare function fetch(input: RequestInfo, init?: RequestOptions): Promise<Response>;

But the spec actually doesn't say that it can be a URL object (meaning Flow models this very common implicit URL to string conversion as done by URL#toString): https://fetch.spec.whatwg.org/#requestinfo

typedef (Request or USVString) RequestInfo;
interface Request {
  constructor(RequestInfo input, optional RequestInit init = {});
  ...
}

...

fetch(RequestInfo input, optional RequestInit init = {});

[mischnic]

Any news regarding this ?
cc @mroch